Treadmills have become very popular for use in improving health and fitness. Many commercially available treadmills include an endless belt that rotates about rollers at each end. The belt may travel across a deck surface that is supported by a frame member. The deck may provide a generally rigid surface. The impact of an individual's feet on a generally rigid surface may create various injuries such as “shin splints” and other leg related problems. Thus, many commercially available treadmills include a cushioning mechanism that dampens the impact force of an exerciser's feet on the deck during an exercise session on the treadmill. Many cushioning mechanisms that may be used to dampen the impact force of a user's feet are well known. Examples of various deck cushioning mechanisms are described in U.S. Pat. Nos. 5,441,468, 7,628,733, 5,279,528, 6,786,852, 7,563,205, and 6,174,267.
While systems that cushion or dampen the impact force of a user's feet on a treadmill deck may help to avoid some injuries, there may be times when an individual prefers to walk, run, or jog on a treadmill deck that is rigid and inflexible. For example, some individuals may use a treadmill to train or otherwise prepare for a race, marathon, or other event that is to occur on a surface that is rigid and generally inflexible, such as cement or pavement. For these individuals, training on treadmill having a generally rigid and inflexible deck may help the individual to prepare his or her body for the actual conditions that will be encountered during the event. On the other hand, training on a treadmill having a cushioned and flexible deck may render the individual not only unprepared for the event but more susceptible to injury during the event.